In recent years, a glass optical fiber of a Single-Mode type (SM type) has been widely used for a long distance trunk line, for the purpose of building an information network. The SM optical fibers have a considerably small core diameter in a range of 5 μm to 10 μm. Therefore, in setting the optical fiber, it is necessary to use means for connecting or branching the optical fiber with high accuracy.
Disclosed by the inventors of the present invention in Japanese Laid-Open. Patent Publication No. 2002-23015 (published on Jan. 23, 2002) is a method for manufacturing an optical fiber connector which allows the optical fiber to be connected or branched with high accuracy by simply forming a lens surface. As illustrated in FIG. 3 an optical fiber connector 29 manufactured in accordance with the method includes a connector main body 30 having a cylindrical shape. At one end of the connector main body 30, a SM optical fiber wire 33 is placed. A fiber 34 drawn from an end of the optical fiber wire 33 is inserted in the connector main body 30. The fiber 34 is implanted in a fiber region of the connector main body 30 with a resin material 31 such as epoxy resin. Thereafter, an ultraviolet light hardened resin 32 is injected in a resin injection portion located at the leading end of the fiber 34. In this way, the optical fiber connector 29 is formed.
As described above, in this publication, a core of the fiber 34 is inserted in the connector main body 30, and the fiber 34 is implanted with the resin material 31 such as epoxy resin. However, the publication does not describe a concrete method for holding the fiber in the connector main body, i.e., a method as to how the optical axis of the fiber can be held at center of the connector main body. Further, because the manufacturing method does not allow the optical axis of the fiber to be held with high accuracy, the method includes the step of adjusting misalignment of the optical axis.
Further, in addition to the foregoing method, there are other methods for holding a fiber, such as a method that uses injection molding to provide a shape that fits the implanted fiber, and a method in which a zirconia ferrule is passed through a pipe. However, these methods have problems in that the former requires a mold for the implantation of the fiber in the connector main body, and that the latter uses expensive zirconia ferrule.
As such, regardless of the type of conventional methods used to insert the fiber in the connector main body, it is very difficult to hold the fiber at the center of the connector while easily and accurately holding the optical axis. Accordingly, in addition to the additional manufacturing step required to correct the optical axis as described above, the procedure is complicated and requires a considerable amount of time. Further, misalignment of the fiber optical axis can cause coupling loss. Therefore, for reduction or prevention of the coupling loss, it is very important to hold the fiber at the center of the connector main body with high accuracy.
Incidentally, optical fiber connectors are connected to each other by aligning the respective ends of the connectors with high accuracy by using a split sleeve or the like. For example, conventional FC connectors are connected to each other by placing a pair of ferrules opposite each other in a sleeve, with the optical fibers held and fixed at the respective centers of the ferrules. The ferrules are then aligned in a straight line to couple the connectors.
Further, in an E/O (electric/optical) or O/E (optical/electric) converter (i.e., optical network unit (ONU)), the fiber is connected to an ONU device by aligning the two using precision components. For example, in the electric/optical conversion, coupling is made by converging emitted light of a semiconductor laser (LD) through a light converging member such as a ball lens placed between the semiconductor laser and the fiber, so as to accurately align the semiconductor laser and an end face of the fiber. Moreover, there is also a method in which the semiconductor laser and the fiber are connected with high accuracy by drawing the fiber to a vicinity of an end face of the semiconductor laser.
However, these connecting methods require precision components, and accurate alignment requires proficiency. Therefore, the operation is impractical. This has caused the conventional optical fiber to be expensive.
The present invention was made in light of the conventional problems, and one of its objects is to provide (i) an optical fiber connector in which an optical axis of the optical fiber can be easily held at the center of the optical fiber connector with high accuracy, and (ii) a manufacturing method thereof, and (iii) a use thereof. Another object is to provide (i) an optical fiber connector that allows for easy and accurate alignment of optical axes, (ii) a manufacturing method thereof, and (iii) a use thereof.